A conventional flip electronic device such as a notebook computer, mobile phone or the like generally has a hinge to couple a display and a body to allow the display to be opened or closed against the body, and also provide torsional force to support and anchor the display at a desired angle after being opened. In the past the hinge usually was a single-axis hinge with only one shaft as an axis. Although the single-axis hinge allows the display to be opened against the body, the display and body interfere each other after the display has been opened at a certain angle and cannot be opened continuously to greater angle, hence a range of open angles of the electronic device is limited. Nowadays touchable electronic devices equipped with a keyboard and a touch screen is very fashionable. Aside from using the keyboard to do input as usual, flipping and stacking the touch screen and keyboard-attached body inversely to input in a touch mode also is a commonly required function. As a result, the conventional single-axis hinge can no longer meet the requirement of present market.
To overcome the flaws of the conventional single-axis hinge, a double-axis hinge capable of rotating to a greater angle has been developed, such as Taiwan patent No. M433709 which discloses a double-axis hinge that comprises a shaft holder, a first shaft and a second shaft disposed in the shaft holder, friction plates penetrated by the first and second shafts to provide frictional forces and fixed friction plates connected to the first and second shafts to rub with the friction plates. The first and second shafts can respectively rotate relative to the shaft holder, and can be installed respectively on a first device body (such as a display) and a second device body (such as a device body) of an electronic device, so as to allow the first device body to rotate against the second device body, and at maximum the first device body can be flipped to the backside of the second device body. While the M433709 double-axis hinge can meet the requirement of a touchable electronic device needed to be opened to a greater angle by flipping, the first and second shafts do not have a mechanism to rotate alternately. Its two shafts could rotate simultaneously. As a result, when the display rotates against the device body, the relative positions of the shaft holder and the device body could also change to make the display tilting backward and give users unsteady feeling when in use.
To resolve to aforesaid disadvantage, producers have developed double-axis hinges capable of rotating in sequence, such as Taiwan patent Nos. M438797, M441303, M442005 and M452593 disclosed. Each of those double-axis hinges generally include a first shaft and a second shaft parallel with each other, a first latch cam and a second latch cam coupled respectively on the first shaft and the second shaft, and a first connection plate and a second connection plate disposed at two sides of the first and second latch cams and run through by the first and second shafts. The first latch cam has a first recess on the perimeter thereof, and the second latch cam has at least one second recess on the perimeter thereof. The first connection plate and second connection plate are interposed by a roller which is disposed between the first and second latched cams and can be movably wedged in the first or second recesses, thereby to switch rotation of the first shaft and the second shaft. In addition, the first and second shafts have respectively a detent portion, and the first connection plate has barriers to block the detent portions to confine rotation of the first and second shafts. On the other hand, Japan patent No. JP5112121 also discloses a dual-axis hinge which comprises a hinge case, a first shaft and a second shaft parallel with each other and run through the hinge case, a first cam and a second cam respectively pierced through by the first shaft and second shaft, a first driven member and a second driven member located between the first and second shafts and being in contact respectively with the first and second cams, and an elastic unit located between the first and second driven members to provide a thrust force. The first cam and the second cam have respectively a plurality of recesses, while the first and second driven members have respectively a boss to latch the recesses. The elastic unit pushes the first and second driven members to latch the boss on the recesses to switch rotations of the first shaft and second shaft. In addition, the first and second shafts also penetrate respectively through a first rotation retainer and a second rotation retainer that can latch respectively on a first rotation restriction portion and a second rotation restriction portion formed on the hinge case to restrict rotations of the first and second shafts. Although the aforesaid double-axis hinges can make the first and second shafts rotate sequentially to maintain stabilities during opening or closing, their structures are complex and have to collaborate with a great number of components during assembly and installation. As a result, they have disadvantages such as complicated production process, difficult assembly and higher fabrication costs.
In recent years some producers have developed a simpler double-axis hinge that can rotate in sequence, such as China patent No. CN202484069 and U.S. patent publication No. US2013/0135809. They all disclose a hinge device which includes a hinge bracket, a first axis and a second axis that are parallel with each other and rotatablely supported by the hinge bracket, and a floating locating member which is supported by the hinge bracket and able to slide between the first and second axes. The first and second axes have respectively a first recess and a second recess. The floating locating member can be coupled respectively to the first recess and second recess to make the first and second axes to rotate sequentially. Further, each of the first and second axes also forms a protrusion, and the hinge bracket has stop parts corresponding to the protrusions to stop rotation of the first and second axes at a preset angle. In addition, Taiwan patent publication Nos. 201326589 and 201326590 also disclose a lock type dual axis hinge which includes a connecting frame, a first rotation shaft and a second rotation shaft being pivoted to the connection frame side by side, and a first latch recess and a second latch recess formed respectively on the first rotation shaft and second rotation shaft. The connection frame has a holding aperture located between the first and second latch recesses to hold a floating member which is engage respectively with the first latch recess and second latch recess to allow the first rotation shaft and the second rotation shaft to rotate in sequence. The floating member can be a pin with two spherical ends or two rolling balls. The first and second rotation shafts further respectively through a first detent plate and a second detent plate, and the connection frame includes a first barrier and a second barrier to block the first and second detent plates to confine the rotation angles of the first and second rotation shafts.
The hinge devices and the lock type dual axis hinges in the aforesaid CN202484069 and US2013/0135809, and Taiwan 201326589 and 201326590 have simpler structures, but shapes of their components are complicated which generates serious tolerance problems. For instance, in the hinge devices disclosed in CN202484069 and US2013/0135809, the first and second recesses are formed in an arched shape, hence fabrication thereof is more difficult and the problem of machining tolerances easily occurs that could decrease degree of precision. In Taiwan 201326589 and 201326590, the parts of the floating member which contacts with the rotation shafts and the latch recesses are arched tangent surfaces formed axially on the floating member. Thus, fabrication of the floating member also is difficult and costly, and precision of the finished product is hard to control. Moreover, when the floating member latches on the latch recess they merely contact in a small area and form an unstable butting relationship. Hence the surface of the latch recess cannot firmly push the floating member. As a result, when the floating member escapes the latch recess wobbling or movement interruption easily occurs. In addition, the floating member also contacts with and butts the rotation shaft in a small area, therefore the uneven applied force or local wearing could happen to generate deformation of the floating member. Hence the aforesaid hinge devices and the lock type dual axis hinges not only have components formed in complicated shapes that results in higher production costs and lower precision, also have unstable contact between the floating member and axis or unsecure latch relationship between the floating ember and the recess that could cause unsmooth movement of the floating member to result a unstable operation of opening or closing and a undesirable operation feel.